Optimizer Statistics Gathering – pending and history
https://www.dbi-services.com/blog/optimizer-statistics-gathering-pending-and-history/
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create user XIZOR identified by secret;
grant connect, resource to XIZOR;
grant unlimited tablespace to XIZOR;
grant select any dictionary to XIZOR;

connect XIZOR/secret

create table DEMO as select rownum n from dual;

col analyzed for a30
col published_prefs for a30

select num_rows,cast(last_analyzed as timestamp) analyzed,dbms_stats.get_prefs('PUBLISH',owner,table_name) published_prefs from dba_tab_statistics where owner='XIZOR' and table_name in ('DEMO');


insert into DEMO select rownum n from xmltable('1 to 41');


set pages 999 lines 200

select /*+ gather_plan_statistics */ count(*) from DEMO;

select * from table(dbms_xplan.display_cursor(format=>'basic +rows +rowstats last'));

exec dbms_stats.set_table_prefs('XIZOR','DEMO','PUBLISH','FALSE');


exec dbms_stats.gather_table_stats('XIZOR','DEMO');


select num_rows,cast(last_analyzed as timestamp) analyzed,dbms_stats.get_prefs('PUBLISH',owner,table_name) published_prefs from dba_tab_pending_stats where owner='XIZOR' and table_name in ('DEMO');

exec dbms_stats.delete_pending_stats('XIZOR','DEMO');

exec dbms_stats.publish_pending_stats('XIZOR','DEMO',no_invalidate=>false);

exec dbms_stats.set_table_prefs('XIZOR','DEMO','PUBLISH','TRUE');

exec dbms_stats.restore_table_stats('XIZOR','DEMO',sysdate-1,no_invalidate=>false);



select report from table(dbms_stats.diff_table_stats_in_history('XIZOR','DEMO',sysdate-1,sysdate,0));

select 
	end_time,end_time-start_time,operation,target,
	regexp_replace(regexp_replace(notes,'" val="','=>'),'(||)',' '),
	status 
from 
	DBA_OPTSTAT_OPERATIONS where regexp_like(target,'"?'||'XIZOR'||'"?."?'||'DEMO'||'"?') order by end_time desc fetch first 10 rows only
/


select table_name,stats_update_time from dba_tab_stats_history where owner='XIZOR' and table_name='DEMO';

set long 2000000
set pagesize 1000

select * from table(dbms_stats.diff_table_stats_in_history(
                    ownname => 'XIZOR',
                    tabname => 'DEMO',
                    time1 => systimestamp-1,
                    time2 => systimestamp,
                    pctthreshold => 0));